Supermodel Miranda Kerr was not fired as a Victoria’s Secret Angel for “being difficult” but is stepping down because she could not devote enough time to the demanding brand, sources exclusively tell Page Six.

Talks between the lingerie line and the Australian beauty fell apart last week because VS was asking busy model Kerr to devote three months a year to promoting their sexy brand.

But a source with knowledge of the situation told us: “The problem was the time commitment. Victoria’s Secret usually asks the girls who are Angels to commit three months in a particular year to the brand.

“But Miranda has become a big star — she recently signed a deal with airline Qantas and has just replaced Kate Moss as the face of Spanish fashion line Mango,” our source continued.

“While she loves Victoria’s Secret, the time commitment they needed from her as an Angel became too much for her to fulfill. Exactly the same thing happened with Gisele Bundchen and Heidi Klum — their careers became huge, and there were other opportunities which made being an Angel full-time impossible.

“Anyone who says otherwise about Miranda, it’s just sour grapes. She is still going to walk in the show this year, and is still committed to the brand, but their relationship is evolving.”

Other sources tell us Kerr, who has a 2-year-old son, Flynn, with husband Orlando Bloom, also needs the freedom to travel to be with Bloom when he’s filming on location. Her rep declined to comment.

While media insiders whisper that a story of Kerr “being difficult” was planted by those with an ax to grind, Victoria’s Secret’s chief marketing officer Ed Razek leapt to her defense.

He said in a statement,“Miranda Kerr is one of the best models in the history of the business — and easily one of the most popular. She is also a consummate professional. Any rumors to the contrary are simply untrue. We have no plans to stop working with her.” Razek added that Kerr will still walk the runway in the 2013 show.